Most of the drones that have begun to appear in the skies above the U.S. homeland don't resemble the Predators or Reapers flown by the U.S. military and CIA above Afghanistan and Pakistan. Instead, these smaller versions of flying, unmanned vehicles almost rival the animal kingdom in their diversity.

Government agencies such as NASA and U.S. Customs and Border Protection operate aircraft-size military drones that take off from runways like airplanes. Labs in the United States have even built tiny drones that look like hummingbirds. But most drones resemble the radio-controlled aircraft and toy helicopters flown by hobbyists for decades, capable of taking off horizontally, vertically or by being thrown into the air like a trained falcon or hawk.

"To say they're all the same is not accurate at all,” said Kevin Lauscher, an industrial sales representative for Draganfly Innovations Inc.

The U.S. Federal Aviation Administration does not plan to permit drones armed with weapons in U.S. civilian airspace, according to an official quoted by the Washington Times. But state agencies, sheriff's offices and universities have already found more widespread use for drones that carry cameras for taking photos or video from above.

"If you look at the capabilities, there are small, quad helicopters and rotor helicopters that can be fitted with a camera and fit in the palm of your hand," Lauscher told TechNewsDaily. "They go all the way up [in size] to a Global Hawk,” which is a relatively large military drone.

Draganfly Innovations builds small drones weighing less than 5 pounds that fly under the control of a human operator using two joysticks. The Canadian company has sold some drones to law enforcement for taking pictures or video of traffic accidents or crime scenes, as well as aiding SWAT teams preparing to storm a building or housing compound. [7 Next Generation UAVs]

But law enforcement represents a relatively small part of Draganfly's business. Many more clients use drones to cheaply inspect the exterior of huge factories, manufacturing facilities or construction sites. Drones could even help check on tall structures such as wind turbines, Lauscher said.

FAA drone license applications tracked by the Electronic Frontier Foundation, a nonprofit digital rights organization, suggest many other possible uses. Some U.S. states have begun considering drones for checking on highway traffic conditions, inspecting bridges and fighting wildfires. U.S. corporations, such as FedEx, have already begun planning for the day when drones could deliver packages.

Unlike free-flying birds, practically every unmanned aerial vehicle known as a drone flies under some form of human remote control. But university labs have already shown how pre-programmed drones can carry out intricate flight patterns, and military-grade drones have emergency backup routines in case they lose the signal connection to their human operators.

Bird watchers accustomed to spotting a gaggle of geese or a murder of crows may someday spot similar groupings of drones. Such drone swarms will likely use advanced forms of today's artificial intelligence programs to coordinate their missions without precise human control, a future with possibilities both delightful and daunting.